Answer: 1. Thermal Excitation: Electrons can be emitted from a conductor when it is heated to high temperatures and the energy generated is enough to break the bond between the electrons and the atoms in the conductor.
2. Electrical Excitation: When a conductor is subjected to a strong electric field, electrons can be emitted as a result of the field's strength. This is known as the field emission effect.
3. Photoelectric Effect: Electrons can be emitted from a conductor when it is exposed to light, especially ultraviolet light. This effect is known as the photoelectric effect.
4. Electron Bombardment: Electrons can be emitted from a conductor as a result of bombardment by other high-energy electrons. This process is known as secondary electron emission and is commonly used in electron microscopy.
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